From an ergonomic point of view, it is an advantage during long working hours that it is possible for an operator to shift his working position between a sitting position and a standing, or at least partially standing, position. Shifting working position makes sure blood circulation and the general comfort of the user are maintained. At the same time it is a requirement that operator chairs should be possible to adapt to users of different sizes and/or anthropometries (proportions) so as to ensure satisfactory ergonomics. For adapting an operator chair to users of different anthropometries, it is desirable to be able to adjust the operator chair according to the user's length of lower legs, length of thighs, length of underarms and height of elbows. However, it has been shown to be very challengeable to combine ergonomic shifting of working position with a plurality of anthropometric settings in a satisfactory manner.
Wheelchairs and hospital beds are known for making use of various solutions for shifting between sitting/laying positions and standing positions, both manually and power-assisted. Different solutions are also known that shift the angle of a seat while maintaining a constant backrest angle. However, the known solutions do not combine the possibility to shift position with a plurality of anthropometric adjustments/settings. In particular, none of the known solutions maintain the anthropometric settings while shifting the position of the chair/bed between a sitting/laying position and a standing position as well is in any intermediate position.
In operator chairs according to the prior art, the height of the chair has normally been adjustable by means of a linear lifting column. The required lifting height, which typically is in the order of half a meter or more, requires the use of telescopic linear guides and actuators that also need to extend down through the floor in order to achieve a required overlap between linearly gliding parts. The whole linear construction also needs to be protected by telescopic covers to ensure the safety of the user. In sum this makes the lifting arrangement of the chair very large, and thus very unpractical for a chair that is to be of use to operators of different sizes and anthropometries.
A further challenge with operator chairs according to the prior art, including those with a linear lifting column, is the positioning of internal cables and cable guides. Excessive movement and bending of cables lead to wear and reduced lifetime. In a standard, linear lifting column, the cable guide will be hanging freely in a U-shape inside the column, and then move half the distance of the chair while it's lifted and lowered.